Cast aluminum Bracket Cap connects to the top of U-Channel or 1 3/4- to 2-inch Square Post. Designed for use with 8-, 9- or 12-inch tall Street Name signs. The 12-inch slot is for signs up to 42 inches wide; the 18-inch slot for signs up to 54-inch wide; and the 24-inch slot is for signs wider than 54 inches. The 18- and 24-inch size slotted brackets available for Flat blades only, not Extruded.